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Accessory Dwelling Units (ADUs) in California: rules in 10 towns compared
Can I build an ADU (in-law apartment, guest house, garage apartment)? Here's how each town answers it. Click a town for the details and the exact ordinance text.
Last reviewed
This page is for California homeowners planning a backyard cottage, garage conversion or junior ADU. California's ADU law (Gov. Code §§66310–66342, most recently amended effective January 1, 2026) overrides conflicting city rules, including in charter cities. Cities must approve ADUs ministerially, with no hearing, within 60 days of a complete application. They can't require the owner to live on site (except for a junior ADU that shares a bathroom), set a minimum lot size, or demand side or rear setbacks over 4 feet for a new ADU. On a single-family lot you can build one converted ADU, one junior ADU of up to 500 sq ft inside the house, and one new detached ADU of up to 800 sq ft by right. AB 956, which takes effect January 1, 2027, raises that to two new detached ADUs per single-family lot.
Every one of the 10 cities we cover for this topic allows ADUs through a ministerial permit, and all of them bar renting an ADU for less than 30 days. Six (Lafayette, Los Altos, Los Gatos, Manhattan Beach, Pasadena and Saratoga) allow a detached ADU of up to 1,200 sq ft, while Del Mar, Hillsborough, Piedmont and Tiburon top out at 1,000 sq ft for larger units. Los Altos and Saratoga allow up to two junior ADUs. Del Mar's municipal code still says the owner must live on the property, a rule state law may override. Pick your city below for the details and the municipal code text.
Town-by-town comparison
| Town | Verdict | Short answer |
|---|---|---|
| Los Altos | Allowed with a permit | Yes. Los Altos allows ADUs on single-family lots with ministerial approval within 60 days: one attached ADU, one detached ADU (up to 850 sq ft for one bedroom or 1,200 sq ft for two or more, 18 ft tall, 4-ft side and rear setbacks) and up to two junior ADUs of 500 sq ft inside the house. Owner occupancy is required only for a JADU. |
| Saratoga | Allowed | Yes. On a lot with a single-family home, Saratoga allows one ADU inside or attached to the house (or in an existing accessory structure), up to two junior ADUs, and one new detached ADU. A detached ADU can be up to 1,200 sq ft if it stays out of the side and rear setback areas, or up to 1,000 sq ft with 4-foot side and rear setbacks (800 sq ft is always allowed), and up to 16 feet tall. No owner-occupancy is required for an ADU, only for a junior ADU, and the City must decide a complete application within 60 days. |
| Los Gatos | Allowed with a permit | Yes. On a single-family lot Los Gatos allows one ADU plus one junior ADU (up to 500 sq ft inside the house), approved ministerially through a Building Permit within 60 days. ADUs can be up to 1,200 sq ft, one story, and 16 feet tall if detached, with 4-foot side and rear setbacks; the owner must live on site only when there is a junior ADU. |
| Tiburon | Allowed with a permit | Yes. Tiburon allows ADUs in every residential zone through a ministerial building permit decided within 60 days, with no hearing. A typical detached ADU can be up to 850 sq ft (one bedroom, lot under 10,000 sq ft) or 1,000 sq ft (two or more bedrooms, or a larger lot) and 16 feet tall, with 4-foot side and rear setbacks. A junior ADU of up to 500 sq ft inside the house is also allowed. |
| Piedmont | Allowed with a permit | Yes. ADUs are a permitted use in Piedmont's single-family Zone A, approved ministerially (no hearing) by the Planning Director within 60 days. A detached ADU can be up to 850 sq ft (1,000 sq ft with more than one bedroom) and 18 feet tall, at least 4 feet from side and rear lot lines, with no parking required. |
| Lafayette | Allowed with a permit | Yes. Lafayette allows ADUs on single-family lots: a detached ADU up to 800 sq ft (16 ft tall, 4-ft side/rear setbacks) or a conversion inside the house needs only a building permit, and larger units up to 1,200 sq ft get a ministerial ADU permit within 60 days. ADUs have no owner-occupancy requirement but can't be rented for under 30 days. |
| Manhattan Beach | Allowed with a permit | Yes. Manhattan Beach allows ADUs on single-family lots in all Area Districts with a ministerial ADU permit (no public hearing) plus a building permit. Studio and 1-bedroom ADUs can be up to 850 sq ft and 2+ bedroom ADUs up to 1,200 sq ft, with 4-foot side and rear setbacks and a 16-foot height limit for a detached unit. |
| Pasadena | Allowed with a permit | Yes. Pasadena allows ADUs on any lot zoned for homes that has a house, with a ministerial (no-hearing) permit. A single-family lot can have one new attached or detached ADU, one conversion ADU and one junior ADU; a new ADU up to 800 sq ft needs only 4-ft side and rear setbacks, and a larger detached ADU can be up to 1,200 sq ft. |
| Del Mar | Allowed with a permit | Yes. Del Mar allows one ADU plus one junior ADU on a single-family lot. You'll need a building permit and, in many cases, an administrative Coastal Development Permit, both approved by staff without a public hearing. A detached ADU can be up to 850 sq ft (1,000 sq ft with more than one bedroom) and 16 feet tall, with 4-foot side and rear setbacks. |
| Hillsborough | Allowed with a permit | Yes. ADUs are permitted on Hillsborough residential lots with an ADU permit and building permit, approved without a hearing within 60 days. A new detached ADU up to 800 sq ft and 16 ft tall with 4-foot side/rear setbacks qualifies under the state-standard track; larger units (up to 850 sq ft, or 1,000 sq ft with 2+ bedrooms) must meet extra local design standards. |
California's statewide ADU law
California's ADU law (Gov. Code §§66310–66342, recodified from §65852.2; latest amendments effective January 1, 2026) overrides conflicting city rules, including in charter cities. Cities must approve ADUs ministerially (no hearing) within 60 days of a complete application, or the permit is deemed approved.
What cities cannot require or do:
- Owner-occupancy for an ADU.
- A minimum lot size.
- Side or rear setbacks over 4 feet for a new ADU, or any setback for a converted existing structure.
- Size, lot coverage or floor-area rules that block an ADU of at least 800 sq ft. Size caps can't be under 850 sq ft (1,000 for 2+ bedrooms).
- Parking within half a mile walking distance of public transit, or replacement parking for a garage converted to an ADU.
- Impact fees on ADUs of 750 sq ft or less.
By right on a single-family lot: one converted ADU plus one junior ADU (JADU, up to 500 sq ft inside the house), plus one new detached ADU (up to 800 sq ft, 16 ft tall). Owner-occupancy may be required only for a JADU that shares a bathroom.
Short-term rentals: cities may bar ADU rentals under 30 days, and must for by-right ADUs, JADUs and SB 9 units.
Coming January 1, 2027: AB 956 raises the by-right count to two new detached ADUs per single-family lot.
SB 9 (§§65852.21, 66411.7) allows two homes on a single-family lot, or a split into two lots of at least 1,200 sq ft (with a 3-year owner-occupancy affidavit).
Common questions about adu rules in California
- What is the ADU law in California?
- California's ADU law (Gov. Code §§66310–66342) requires cities to approve ADUs ministerially, with no hearing, within 60 days of a complete application, or the permit is deemed approved. On a single-family lot you can have a converted ADU, a junior ADU and a new detached ADU of up to 800 sq ft by right. The law overrides conflicting city rules, including in charter cities.
- How big can an ADU be in California?
- It depends on your city, but there's a floor. A city can't use size, lot coverage or floor-area rules to block an ADU of at least 800 sq ft, and its size cap can't be under 850 sq ft (1,000 sq ft for two or more bedrooms). In the cities we cover, caps for a detached ADU run from 1,000 sq ft (Del Mar, Piedmont, Tiburon) to 1,200 sq ft (Los Altos, Los Gatos, Pasadena, Saratoga).
- Do I need a permit to build an ADU in California?
- Yes. You'll need at least a building permit, and many cities also issue a separate ADU permit, but the review is ministerial: no public hearing, and a decision within 60 days of a complete application. In the coastal zone you may also need a coastal development permit; ask your city's planning department.
- Does California require the owner to live on the property with an ADU?
- No, not for an ADU. State law bars cities from requiring owner-occupancy for an ADU. A city may require it only for a junior ADU that shares a bathroom with the house. If your city's code still has an owner-occupancy rule for ADUs, state law may override it.
- What is the difference between an ADU and a JADU in California?
- A junior ADU (JADU) is a unit of up to 500 sq ft built inside the existing house, while an ADU can be attached, detached or a converted structure. You can have one of each on a single-family lot by right. Starting January 1, 2027, AB 956 allows two new detached ADUs per single-family lot.
- Can I rent my ADU on Airbnb in California?
- Usually not. Cities may bar ADU rentals of under 30 days, and they must do so for by-right ADUs and JADUs. All 10 cities we cover for this topic set a 30-day minimum rental term for ADUs.
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